Radio telegraphy and telephony receiver.



RADIO TELEGRAPHY AND TELEPHONY RECEIVER. APPLICATION mm APR. 11.1914.

1,144,969 Y 1 PatentedJuneQS), 1915."

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G. W. PICKARD. RADIO TELEGRAPHY AND TELEPHONY RECEIVER. APPLKCATIONFILED APR.17,1914.

l 1%% 969@ Patented June 29, 1915.

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RM'BIQ TELEGRAPH? AND TELEPHQNY REGEIVEE.

igiddfiti Specification of letters Patent.

Fatented dune 2%, i915.

application iflflll. April 1.7, 191d. Serial No. 232,592.

To all whom it may concern Be it known that l, Gnnunnnar WirrrrrnnPICKARI), a citizen of" the United States of America. and a resident ofthe town of Ameshury, State of Massachusetts, have invented certain newand useful Improvements in Radio Telegraphy and Telephony Receivers, theprinciples of which are set forth in the following specification andaccompanying drawings, which disclose the form of the invention which Inow consider to he the best of the various forms in which the princinlcsof the invention may be embodied.

This invention relates to a system or method of receiving intelligencecommunintcd by electromagnetic waves, the object being a more ellicientsystem of this kind, the invention consisting; of the apparatus andmethods herein disclosed.

Of the drawings, Figures 1 and 2 are explanatory diagrams; Figs. 37inclusive are diagrammatic illustrations of several of the varioususeful embodiments of the invention.

The description will be in terms of receipt of continuous or undampedwaves with which the invention is most eflicient.

A simple embodiment is shown in Fig. 3 wherein the natural period of theantenna- ,rzround connection A, L, G, the natural period of the closedresonant circuit C U, and the coupling of these two circuits(variable-as indicated by the double arrows) are such, that twooscillating currents of frequencies, which differ from each other, areset up in this svstem when the same is affectcd by transmittedelectromagnetic waves which are not materially damped. These twofrequencies act together to form heats, which have a lower order offrequency as a,

Z), c. in Fig. 1. the energy periodically rising and falling asindicated. Thus if the oscillating current frequency in one of theabove-specified circuits of Fig. 3 is of the order of several tens ofthousands per sec-' 0nd. and if the frequency of the other is of a likeorder but slightly lower. then the heat-frcqucncv mav correspond withthat of audible sounds. This heat-frequency. even when caused to be suchas to correspond with sound frequencies within the limits of audihilitv,will not of itself produce audible sounds in the electromagnetictelephone receivers T (Fig. 3) for the reason that each I in Fig.

beat comprises a group of oscillations of the much higher frequency 2'.c. of the order of several tens of thousands per second, which is farbeyond the limits of audibility, and which would not properly operatesuch a direct current instrument as such telephones. in order to convertthe energy of these heats into sound waves of audible frequency, 2'. e.first, in order to cause it to assume such form as will eliectivelyoperate the telc phones. the heat oscillations are rectified (if-lg. 3)by the connection of the rectifier l) to the coil if (that is, to thatpart of this coil which extends to the right beyond the connection to itof antenna A). This rectifying device B may he of any suitable hind,such for example, as the well-known types of crystal rectifier or gasrectifier heretofore used in this art, as detectors. The resulting:rectified pulses which operate the telephones 'l are indicated in Fig. 2at 11. 71, c Thus we have, first, the original frequency of the undampedelectromagnetic waves as N transmitted through the ether and received ata given receiving station;

second, we have at that rcceiviug'station an arrangement of circuitssuch as those shown 3 at A, L, G, and at L whereby said originalfrequency is converted into two slightly different frequencies (say Nand N which produce heats indicated in Fig. 17 and third. w have ameans, such as rectiher D (Fig. 3) whereby the beat oscillations arerectified so as to obtain the energy; in most eliicient form to operatethe telephones T and produce an audible com munication which has a pitchcorresponding with the frequency of the beats. To explain the inventionin greater detail. assume that the two principal circuits of Fig. 3 (2'.c. the antenna-ground circuit and the closed resonant circuit L. U) eachhas the same natural period N due to its capacity, inductance andresistance, this period being the same as that of the trans mittedwaves: and assuming further that the coupling of these two circuitshas acoefficient K. It is well known that in such a system two oscillatingcurrents will be set up of frequencies diiiering from each other,frequency N being e ual to N divided by the square root of l plus one,and frequency N being equal to N divided by the square root of one minusK. -According to my observation, these two frequencies N ice and Napproach to the common period N in proportion as the coupling of the twocircuits in the system is made loose and the period of the resultingbeats is so low as to be below the lower limit of audibility. Butreversely, as the coupling is made tighter, these two frequencies morewidely differ, with the result that the produced beats have a higherfrequency. In accordance with this invention, a coupling is em ployedwhich causes the production of beats which are of not too high frequencyor too low frequency to be outside the limits of audibility. When thecoupling is too loose,

the current resultingin the telephones from the rectified oscillationsof the beats of low frequency corresponding to such loose coupling, willbe a smooth, continuous current which fails to operate the telephones toproduce an audible sound. .Under this condition a tightening of theadjustable coupling between the coils L and L (Fig. 3) results in anincrease of the beat-frequency so that when ,the proper adjustment ofcoupling is obtained, the formal continuous current in the telephonewindings will begin to pulsate; and as the beat-frequency rises abovethe lower limit of audibility, the" telephones T, receiving therectified current from instrument D, willemit notes corresponding to thefrequency of the beats.

This method is efiicient for working with undamped waves produced by thewell known transmitters of such waves, such as those including an are,or an alternator of the frequency of the order of tens of thousands. Themethod can also be used, however, with spark transmitters, particularlythose having slight damping.

Fig; 4-diifers from Fig. 3 in having an inductive relation of thecircuit DT with the coil L by way of the coil'L and in having thiscircuit grounded. as shownyat G. In any case where such an inductiverelation is employed, the coupling between coils L and L may be variedor adjusted if desired. In Fig. 5 also the relation of circuit DT isinductive to coil If by way of coil L", but circuit DT is not mounted asin Fig. 4, and is provided with a'battervpotentiometer circuit B-P. InFig. .6 the coil L is conductively related to coil L by way of rectifierD and by the circuit of the telephones T, battery B and potentiometercoil P.- In all of Figs. 36 inclusive, the connection of the circuits DTand the inductance coil or coils is uni-lateral, this connectionbeing'made in Fig. 3 to the right hand end of coil L, i. e. the partextending to the right beyond the connection thereto of antenna A; in-Figs. 4 and 5 thisconnection is made to one end of coil L and-in Fig.6'this connection is made between the right hand end of coil L and theleft hand end of the open-circuited coil L. In Fig.

7, however, the method is employed in a system involving a closedcircuit cooperating with the antenna coil L in the open circuit A, L, G,which is preferably, adjusted to the periods of the transmitted waves.Here circuit C, L itself is adjusted to the same frequency, but has avariable coupling with coil L If this coupling is of the proper degree-of tightness, as above explained, the beat-frequency set up will besufliciently high to be within the limits of audibility. The coil L",here as in the other figures, is a pick-up coil for the beat-pulses, andthis coil passes said pulses on to the rectifier D which converts theoscillations composing each heat into the proper form to operatetelephones T. In this case, however, the circuit of the pick-up coil isnot open and is closed through condenser C and this circuit may, ifdesired, have the same natural period as those of the circuits of thecoils I and L obtained as by adjustment of coil L or condenser C orboth. Here this circuit L, C is shunted by the rectifier-telephonecircuit DT wherein the telephones are shunted by the condenser C.

In Figs. 4, 5, and 6, the coil L corresponds with the pick-up coil L ofFig. 7, and in Fig. 3 the coil socorresponding is the right hand part ofcoil L which extends beyond the connection of antenna A.

As indicated above, the general system and method of this invention ismore efficient in proportion as the transmitted waves are substantiallyundamped, being most efiicient with the continued or undamped waveswhich are emitted from a transmitter employing an are or an alternatorof the high frequency hereinbefore specified. However, the method isalso useful in receiving waves which are radiated from transmittersincluding a spark gap provided that such waves are not too highlydamped.

I claim: 1. In a system of communicating intelli- 'gence byelectromagnetic waves which are not materially damped, the combination,at a receiving station, with means for causing such waves of a givenfrequency to set up oscillating currents of two frequencies differingfrom each other to such extent as to produce beats of audible frequency,of means for causing the energy of said beats to produce a sound of apitch corresponding to the frequency of the beats.

2. In a system of communicating intelli gence by electromagnetic waveswhich are not materially damped, the combination, at a receivingstation, with means for causing such waves of a given frequency to setup oscillating currents of two frequencies differing from each other tosuch extent as to produce beats of audible frequency, of means forrectifying the oscillations composing said beats, and a telephonicdevice menace operable by the rectifiedbeat-pulses to pro duce a soundhaving a pitch corresponding to the beat-frequency.

3. In a svsteni of communicating intelligence by electromagnetic waveswhich are not materially damped, the combination, at a receivingstation, with two resonant circuits having such periods and coupling asto cause such waves of a given frequency to set up oscillating currentsof two frequencies differing from each other to such extent as toproduce beats of audible frequency; of a pick-up coil arranged toreceive said beat-pulses; means for rectifying the oscillationscomposing said beats; and a telephonic device operable by the rectifiedbeat-pulses to produce a sound having a pitch corresponding to thebeat-frequency.

4; In a system of communicating intelligence by electromagnetic waveswhich are not materially damped, the combination, at a receivingstation, with two resonant circuits having such periods and coupling asto cause such Waves of a given frequency to set up oscillating currentsof two frequencies differing fromeach other to such extent as to producebeats of audible frequency;

of a pick-up coil arranged to receive said beat-pulses; of means forcausing the energy of said beats to produce a sound having a pitchcorresponding to the frequency of the heats. v

5. In a system of communicatin intelligence by electromagnetic waves wich are not materially damped, the combination, at a receiving station,with means for causing such waves of a given frequency to set uposcillating currents of two frequencies differing from each other tosuch extent as to produce beats of audible frequency, of a pick-up coilarranged to receive said beatpulses; and means unilaterally connected tosaid pick-up coil, and operable by the energy of said beat-pulses, toproduce a sound having a pitch corresponding with the frequency of thebeats.

GREENLEAF WHIITIER PICKARD. Witnesses:

M. C. HANNON, W. F. BARKLEY.

